When you delete the product, this remain in database. So in database are all products you ever add.
I have the latest version 2.0.0 and I try to import products from version 1.1.9.
I deleted tested products from 2.0.0 in administrator but when i check in database in table `zlz6v_virtuemart_products_en_gb` they are all there. I have to delete them manually from database.
BR
Vitja